The present invention generally relates to a field of manufacturing of electronic products, and more specifically, to a rework method and a temperature triggering ejector mechanism for a lock pin soldering type component.
Currently, for assembling of an electronic product, the process including the following steps is generally adopted: print→mount→reflow solder→wash→check→rework. When a defect is detected in an electronic product, the electronic product is not directly scrapped, but reworked. The electronic product is reworked to eliminate the defect, so as to improve the yield and reduce the production cost.
Lock pin are configured in some components of the electronic product to provide extra mechanical strength for the interconnection between the components and a circuit board (or an electronic card assembly). Such lock pins are fixed (stuck) in through holes (such Plating Through Holes (PTHs) of the circuit board (such as Printed Circuit Board (PCB)). FIG. 1 shows a perspective view of an electronic component with lock pins, which is to be mounted on a circuit board.
FIG. 2 is a schematic diagram showing an electronic product that has been finished manufacturing. In FIG. 2, lock pins of the component in the upper portion are stuck at through holes of the PCB in the lower portion. There are “fish-eye” portions bending outwards in the middle of lock pins. The overall width of “fish-eye” portions is slightly larger than the diameter of through holes, so that when lock pins are inserted into through holes, lock pins are compressed and deformed to generate elastic force in a direction that is opposed to the direction of deformation. With the elastic force, lock pins will push against the hole walls of through holes. In this way, when the component is being pulled up from the circuit board, friction force will be generated between lock pins and hole walls of through holes. This friction force ensures that the component is firmly fixed on the circuit board. However, during a rework process, this friction force makes it difficult to remove the component from the circuit board, and may cause damage to the component or the circuit board.
FIG. 3 is a schematic diagram showing the electronic product in FIG. 2 during a rework process. In FIG. 3, when removal force F1 is applied to the component in the upper portion of FIG. 3, friction force F2 will be generated in the PTH in a direction that is opposed to the direction of the removal force F1.
In addition, FIG. 2 shows that plating through holes are filled with solder that has been solidified after soldering. Solder also exists between normal pins (Surface Mounted Technology (SMT)) and the circuit board. With lock pins and soldering, the component is fixed on the circuit board more firmly. However, the design of soldering lock pins to PTH holes is a challenge to the rework process. During the rework process, a soldered part needs to be heated by hot gas to melt the solder so that the component can be pulled up from the circuit board. Solder that is heated and melted is shown in FIG. 3.
Currently, in the electronic product assembling industry, known solutions to remove the lock pin type component during the rework process include: manually removing the component body by hand, and a mechanical extractor that grabs hold of the component body and pulls it up, etc. All these existing solutions have limitations as follows: during the elevated solder melting temperature, because of elevation of the temperature (in comparison with the room temperature), the component body will soften and may not provide sufficient pull up force for lock pins of the component; timing for applying the pull up force is not controlled, which however is critical, because application of the pull up force in a case where the solder is cold and solid may cause damage to PTH holes, and/or the component.
In the prior art methods, there is a risk of component removal failure. The failure to remove the component with lock pins or any damages to the PTH holes during component removal may mean a scrap of the entire circuit board.